A multichamber apparatus is used in a semiconductor device production process, where the multichamber apparatus includes a plurality of chambers disposed around a vacuum chamber or, the multichamber apparatus includes a wet processing apparatus with a plurality of processing tanks arranged in series. As discussed above, such apparatus may be used in lot-by-lot processing where one lot is processed after another lot.
In these processing systems, the processing time necessary for a certain current lot is influenced by the processing time necessary for a previous lot which was earlier introduced into the processing system. At the outset, the construction of this type of processing system and the status of operation will be explained.
FIG. 1 is a schematic plan view showing the construction of this type of multichamber apparatus. As shown in the drawing, two load lock chambers 12, one etching chamber 13, one heating chamber 14, and four sputtering chambers 15 are disposed around a separation chamber 11. An autoloader 16 is disposed outside the load lock chambers 12.
Processing using this processing system is carried out as follows. Here it is assumed that the processing time in the sputtering chamber 15 is four times that in the etching chamber 13 and the heating chamber 14. For example, a cassette for a certain lot consisting of 26 wafers (hereinafter referred to as “lot A”) is first carried in the right-side load lock chamber 12 (load lock chamber #1) through the autoloader 16. A first wafer in the lot A is taken out by a robot installed within the separation chamber 11 and is carried in the etching chamber 13. Upon the completion of processing of the first wafer in the etching chamber 13, the first wafer is carried in the heating chamber 14. Subsequently, a second wafer is carried in the etching chamber 13. When the processing of the first wafer in the etching chamber 13 and the processing in the heating chamber 14 has been completed, the first wafer is carried in one of the sputtering chambers, for example, the right-side sputtering chamber (chamber #1) and the second wafer is carried in the heating chamber 14.
Next, a third wafer is carried in the etching chamber 13. When the processing in the etching chamber 13 and the processing in the heating chamber 14 have been completed, the second wafer is carried in one of the sputtering chambers, for example, the second sputtering chamber from the right (chamber #2) and the third wafer is carried in the heating chamber 14. Thereafter, in the same manner as described above, wafers are successively carried in and processed in processing chambers. Upon the completion of processing in the sputtering chamber, the wafer is returned to the cassette within the right-side load lock chamber 12 (chamber #1). When processing has been completed for all the wafers of the lot A and all the wafers of the lot A have been returned to the cassette, this cassette is withdrawn through the autoloader 16 to the outside of the processing system 20. During processing for the lot A using the load lock chamber #1, a next lot to be processed using this processing system (hereinafter referred to as “lot B”) is carried in the load lock chamber #2.
As soon as the processing of the final wafer in the lot A. has been completed and this wafer has been returned to the cassette in the load lock chamber #1, a first wafer in the lot B within the load lock chamber #2 is taken out by the robot installed in the separation chamber 11 and is carried in the etching chamber 13. Thereafter, the remaining wafers in the lot B are successively processed in the same manner as described above in the processing of the wafers in the lot A.
It should be noted that, in the above multichamber apparatus, all the chambers are not alwaysoperable. For example, there is a possibility that, among the four sputtering chambers 15, only two chambers are operable (hereinafter referred to often as “operable chambers”). In this case, as compared with the case where the four chambers areoperable, the processing time necessary for the lot is approximately doubled.
FIG. 2 is a schematic perspective view showing the construction of a wet processing apparatus wherein a plurality of lots are successively introduced. In this processing system 20, seven processing tanks 17 are arranged in series. In the example shown in the drawing, the lot A is processed in all the processing tanks 17, whereas, for the lot B, processing is not carried out in the second and third processing tanks from the left (processing tanks #2 and #3). At the outset, a container, which holds wafers of the lot A, together with the wafers, is carried in and processed in the processing tank #1. Upon the completion of processing in the processing tank #1, the container holding the wafers of the lot A is carried in the processing tank #2. Next, the wafers of the lot B, together with the container holding the wafers, are carried in and processed in the processing tank #1. Upon the completion of processing in the processing tank #2, the wafers of the lot A are carried in and processed in the processing tank #3. Thereafter, in the same manner as described above, the wafers of the lot A are processed in the processing tanks #4 to #7 and are then carried out to the outside of the processing system 20.
On the other hand, for the lot B, even after the completion of processing in the processing tank #1, the lot B is on standby until the lot A is processed in the processing tank #4 and is carried out to the processing tank #5. Thereafter, the lot B is carried in and processed in the processing tank #4, followed by processing in the processing tanks #5 to #7 in the same manner as described above.
FIG. 3 shows an example of the elapse of time in the processing of a plurality of lots using the above processing system. The operation for the lot A is started at time t1, and the operation for the lot B is started at time t2. For lot C, the operation is scheduled to be started at time t3. For the lot A, at time t4, the operation is completed. Upon the start of the operation or upon the end of the operation, these times t1 to t4 are reported from the processing system side to the production control device side. In the processing process as shown in the drawing, the processing time for the lot B (difference between operation end time and operation start time) is possibly influenced by the processing time of the lot A. Likewise, the processing time for the lot C is possibly influenced by the processing time for the lot B. The invention is directed to the prediction of processing time for the lot C which is about to be processed or for which the processing has been started.
In addition to the processing time for the previous lot, for example, the number of wafers contained in the lot, the processing time necessary in each chamber or processing tank, the number of load locks in the processing system, and the number of operable chambers are considered as factors governing the processing time for each lot.
FIG. 4 is a block diagram illustrating a processing method using a conventional scheduler. In FIG. 4, a scheduler 1 inquires concerning the time necessary for processing in the processing system, that is, the processing time, of a processing time data maintaining device 8. Upon the receipt of the inquiry, the processing time data maintaining device 8 returns, to the scheduler 1, information on the type of processing system, in which processing operation is carried out, and an estimated value maintained for each type of operation condition. Based on the received estimated values, the scheduler 1 predicts the end time, and, based on the predicted end time, determines the order of operation of the object lot and the prediction of the operation for the lot. The scheduler 1 gives the prediction of lot operation to the transfer control unit 6. According to the prediction of lot operation, the transfer control unit 6 performs control so that a transfer device 10 transfers, from an automatic tray 9 storing a lot as a processing object, the lot to the processing system 20 where processing is carried out.
The processing operation using the conventional line scheduler has the following problems. The first problem is that the processing time of the system is estimated on the assumption that, independently of the status of the operation of the previous lot, the processing time is a given time for the type and operation conditions for each processing system. Therefore, a difference occurs between the given value estimated for each type of processing system and for each operation condition and the actual processing time which depends upon the status of operation of the previous lot. As a result, the schedule of the lot operation output from the scheduler is different from the actual lot operation. For this reason, the control is performed so that, upon the output from the scheduler, the processing device is on extra standby, or otherwise, the lot, which has been scheduled so as to provide no standby time, is brought to a standby state.
The second problem is that, when parameters are specified in detail, i.e., the time of processing in chamber within the processing system, the time of transfer by the robot within the processing system, the load lock time and the like by the conventional method are specified in detail, wherein a given time is set for each unit operation, to enhance the accuracy of the predicted processing time, the number of processing times to be Bet is very large, making it impossible to manually perform the setting.